The invention relates to surface effect ships such as are hereinafter referred to as "S.E.S.", and which typically include a main hull structure having rigidly depending and longitudinally extending side walls (or "side hulls") extending downwardly from opposite sides thereof. Thus, there is defined therebetween a tunnel or chamber of inverted U-shaped sectional form into which pressurized fluid (air) for "cushioning" the hull of the ship relative to the water line is supplied so that only the lower extremities of the side walls thereof remain in contact with the water for air cushion sealing purposes. Suitable flexible bow and stern seal devices are provided at opposite ends of the ship between the side walls thereof, so as to control leakages therefrom of the cushioning support fluid.
Propulsion for such a ship is typically furnished by means of fully submerged propellers carried by drive shafts inclining downwardly from the planing "keels" of the side walls thereof; said drive shafts being in side view inclined in acute angled relationships with said keels. In order to obtain adequate propeller performance efficiencies, the angles between the propeller shafts and the bottom surfaces of the keels are typically made overlarge in order to sufficiently "clear" the propellers from the keels. However, such overlarge propeller shaft inclination arrangements contribute to excessive ship "draft" or "bottom clearance" problems; and compromises therewith lead to less than suitable propeller operating efficiencies.